Justin Bieber -- Norway Cops Threaten State of Emergency

Police in Norway are on the verge of declaring a state of emergency in Oslo, after tens of thousands of unruly Justin Bieber fans overran the city -- and now, they're begging the singer for help.

Justin's scheduled to perform 4 new songs tonight outside Oslo's famed opera house as part of his "Around the World" TV special -- and we're told crazed Bieber fans from all over Europe have descended on the city for the event.

We're told the crowds have swelled to such overwhelming numbers, the police lost control -- and are pleading with Bieber to take the stage early ... before all hell breaks loose ... as in RIGHT NOW.

Bieber's aware of the situation -- he just tweeted, "...for the show to happen u must all listen to the police. we are all concerned for your safety and i want what is best for u. please listen."

Bieber is currently in a secret location and will be helicoptered to the stage.

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